syslog severity mapping problem

[xjplke]

slog/handler/syslog.go

Line 60 in 70031a7

return h.writer.Info(string(bts))

All slog Level are set to syslog severity Info.
Suggest slog Level to syslog severity as sub：
PanicLevel -> LOG_EMERG
FatalLevel -> LOG_CRIT
ErrorLevel -> LOG_ERR
WarnLevel -> LOG_WARNING
NoticeLevel -> LOG_NOTICE
InfoLevel -> LOG_INFO
DebugLevel -> LOG_DEBUG
TraceLevel -> LOG_DEBUG